纳米CeO2含量对Ni60A涂层组织及耐腐蚀性能的影响

利用激光熔覆同轴送粉技术在TC4合金表面制备了不同CeO2含量的Ni60A复合涂层,以此提高TC4合金的耐腐蚀性.通过XRD、SEM、EDS等对CeO2/Ni60A复合涂层进行了表征与测试,结果表明:适量的稀土氧化物CeO2可以细化晶粒,改善涂层内部的组织分布,并且促进NiTi、Ti2Ni和TiC等增强相的生成;在电化...     

A PTD‐based transaction protocol for public transportation

Advances in wireless network technology and the increasing number of users of the personal trusted device (PTD) make the PTD an ideal channel for offering personalized services to mobile users. In this paper, we propose using a PTD as a payment tool in a mobile transaction system for public transportation. To overcome the inherent weakness of computing resources in a PTD, we use a trusted observer to coordinate the mobile transaction and to integrate cryptology (such as a digital signature and a one‐way hash function). The proposed scheme satisfies the requirements for mobile transactions. These requirements include fairness, non‐repudiation, anonymity, off‐line capability, no forgery, efficient verification, simplicity, and practicability. Because a PTD is more portable and personal than a personal computer and because the public transportation can be a necessity in our daily lives, our scheme proposes a novel use of PTDs in mobile commerce. Copyright © 2008 John Wiley & Sons, Ltd.     

p-GaN/Al0.35Ga0.65N/GaN应变量子阱肖特基紫外探测器

报道了p-GaN/Al0.35Ga0.65N/GaN应变量子阱结构的肖特基紫外探测器的制备及性能.器件的测试结果表明,在p-GaN/Al0.35Ga0.65N/GaN双异质结中强烈的压电极化和Stark效应共同作用下使得器件在正偏和反偏时的响应光谱都向短波方向移动了10nm.零偏下器件在280nm时的峰值响应为0.022A/W,在反向偏压为1V时,峰值响应增加到0.19A/W,接近理论值.在正向偏压下器件则呈平带状态,并在283和355nm处分别出现了两个小峰.在考虑极化的情况下,通过器件中载流子浓度分布的变化解释了器件在不同偏压下的响应特性,发现p-GaN/Al0.35Ga0.65N/GaN中的极化效应对器件的响应特性影响很大,通过改变偏压和适当的优化设计可以使探测器在紫外波段进行选择性吸收.     

折衍混合红外光学系统消热差设计

论述了衍射光学元件的消热差和消色差的温度特性及设计方法,根据折射和衍射光学元件固有特性,设计采用320×256凝视焦平面阵列探测器,工作在中波3~5μm,视场范围为8°×6°的红外系统,该系统使用硅和锗两种红外光学材料。实现了在-40~60℃温度范围内消热差和消色差,像质优良。此系统具有成像质量高、体积小、重量轻、工作温度范围宽的特点,使得折/衍混合光学元件在机载红外成像系统中得到成功应用。     

一种基于相关运算的快速码捕获方法

在多普勒频偏很大的情况下,传统的捕获方法往往耗时很长。传统的捕获方法是直接对采样信号进行FFT变换。提出了一种基于信号相关值的FFT快速捕获方法,该方法结合了直扩系统的信号特点和数字信号处理技术,通过对多个子相关器输出值进行FFT变换,同时测量多个多普勒频偏估计预值,并依据峰值最大所对应的频率估计值对本地载波频率进行调整。而且该方法为全数字方法,可以用FPGA、DSP等处理芯片方便地实现。最后给出了计算机仿真结果,并根据仿真结果分析了该方法的平均捕获时间,其性能优于传统的捕获方法。     

温度和工艺参数浮动下双阈值footed多米诺电路的漏电流特性

考虑到温度和工艺参数浮动的影响,对休眠双阈值footed多米诺电路的漏电流特性进行了系统的量化研究和比较,得到了不同温度下的最佳休眠状态.基于65和45nm BSIM4模型的HSPICE仿真表明:与业已提出的CHIL(时钟为高,输入均为低电平)状态和CHIH(时钟和输入均为高电平)状态相比,本文提出的CLIL(时钟和输入均为低电平)状态更有利于减小低温下电路的漏电流和高温下的多扇人电路的漏电流.而且,分析了工艺参数的浮动对双阈值footed多米诺电路的漏电流特性的影响,并给出了温度和工艺参数浮动下,双阈值footed多米诺电路漏电流最小的休眠状态.     

攻击舰载导弹防空系统的电子战战法

根据信息作战原理,运用仿真和统计学分析的混合方法,建立基于概率的二人零和（TPZS）非合作博弈模型,为海军航空兵设计对舰载导弹防空系统攻击的电子战战法。对一个典型实例的初步研究表明：识别真目标、假目标以及导弹命中目标的概率是评估信息与火力联合打击能力的关键,而对评估结果进行博弈分析则是电子战战法设计的关键。海军航空兵对舰载导弹防空系统的信息子系统和火力子系统电子战攻击的最优战法为χ^＊=（O．2500,0．0000,0．750O）,舰载导弹防空系统的最优电子战攻击防御战法为△^＊=（0．0000,0．70803,0．2917）。     

多用户多天线系统中基于THP的低复杂度调度排序算法

本文提出了下行多用户多天线系统中一种新的基于Tomlinson-Harashima预编码(THP)的低复杂度调度排序算法.该算法根据THP与误符号率的特点,将调度和排序结合在一起,有效降低了复杂度.仿真结果表明,本文提出的算法在平均误符号率性能上逼近贪婪调度best-first排序,而复杂度更低,在实际系统中有很好的应用价值.     

Nanowire-Based Soft Wearable Human–Machine Interfaces for Future Virtual and Augmented Reality Applications

A virtual world has now become a reality as augmented reality (AR) and virtual reality (VR) technology become commercially available. Similar to how humans interact with the physical world, AR and VR systems rely on human–machine interface (HMI) sensors to interact with the virtual world. Currently, this is achieved via state of-the-art wearable visual and auditory tools that are rigid, bulky, and burdensome, thereby causing discomfort during practical application. To this end, a skin sensory interface has the potential to serve as the next-generation AR/VR technology because skin-like wearable sensors have advantages in that they can be ultrathin, ultra-soft, conformal, and imperceptible, which provides the ultimate comfort and immersive experience for users. In this progress report, nanowire-based soft wearable HMI sensors including acoustic, strain, pressure sensors, and physiological sensors are reviewed that may be adopted as skin sensory inputs in future AR/VR systems. Further, nanowire-based soft contact lenses, haptic force, and thermal and vibration actuators are covered as potential means of feedback for future AR/VR systems. Considering the possible effects of the virtual world on human health, skin-like wearable artery pulses, glucose, and lactate sensors are also described, which may enable imperceptible health monitoring during future AR/VR practices.     

High Yield Electrosynthesis of Hydrogen Peroxide from Water Using Electrospun CaSnO3@Carbon Fiber Membrane Catalysts with Abundant Oxygen Vacancy

Hydrogen peroxide (H₂O₂) production by electrochemical two-electron water oxidation reaction (2e-WOR) is a promising approach, where high-performance electrocatalysts play critical roles. Here, the synthesis of nanostructured CaSnO₃ confined in conductive carbon fiber membrane with abundant oxygen vacancy (O_V) as a new generation of 2e-WOR electrocatalyst is reported. The CaSnO₃@carbon fiber membrane can be directly used as a self-standing electrode, exhibiting a record-high H₂O₂ production rate of 39.8 µmol cm⁻² min⁻¹ and a selectivity of ≈90% (at 2.9 V vs reversible hydrogen electrode). The CaSnO₃@carbon fiber membrane design improves not only the electrical conductivity and stability of catalysts but also the inherent activity of CaSnO₃. Density functional theory calculation further indicates the crucial role of O_V in increasing the adsorption free energy toward oxygen intermediates associated with the competitive four-electron water oxidation reaction pathway, thus enhancing the activity and selectivity of 2e-WOR. The findings pave a new avenue to the rational design of electrocatalysts for H₂O₂ production from water.